I have read that mashing at lower temperatures takes longer for conversion (Dave Miller). I've also read that poorly crushed grain takes longer to convert (on this forum). I have also read that the color change with iodine indicate the degree of conversion (Greg Noonan).
I cannot quantify these statements, but when I started mashing at 150F, I did do an iodine test at 60 minutes and 90 minutes. The 60 minute sample turned blue (indicating starch), but the 90 minute test turned yellow (with a faint reddish tint) indicating complete conversion. I cannot even guarantee that the 60 minute test was accurate. There may have been some husk material in the wort sample which could give a false reading.
For me however, this is all academic as it takes me 90 minutes to heat my sparge water for most brews, so I have to sparge for 90 minutes, which works well for me.

-a.

__________________
There are only 10 types of people in this world. Those that understand binary, and those that don't.

A starch test shows positive for starch or not positive. It does not show how.....far the starch is broken down.....it is an indicator that conversion is complete.....not that the sugar profile is where you want it to be, depending. Remember John palmers mashing allegory...maybe only one process has taken place......if I'm correct sugars are further degraded by specific enzymes from longer chain sugars, temp and time affect on how far they are degraded. Thus a longer mash...,further degradation and better attenuation....more simple sugars. So yes conversion can be complete......but the degree of the sugar profile in the wort is dependent beyond that.

Remember enzymes are active over an overlapping range......so you time will be more dependent on temps....and your wort profile will be dependent as well......but more so at lower temps.

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its fkin close to water.
Lagering/conditioning: German pils, Dortmunder
Lagering:Kolsch, Dusseldorf alt
American Amber, Red ale
Double ipa, Rye ipa
Fermenting: German pils
Wheat 1,Wheat 2
All to be kegged and served by May 10

I have read that mashing at lower temperatures takes longer for conversion (Dave Miller). I've also read that poorly crushed grain takes longer to convert (on this forum). I have also read that the color change with iodine indicate the degree of conversion (Greg Noonan).
I cannot quantify these statements, but when I started mashing at 150F, I did do an iodine test at 60 minutes and 90 minutes. The 60 minute sample turned blue (indicating starch), but the 90 minute test turned yellow (with a faint reddish tint) indicating complete conversion. I cannot even guarantee that the 60 minute test was accurate. There may have been some husk material in the wort sample which could give a false reading.
For me however, this is all academic as it takes me 90 minutes to heat my sparge water for most brews, so I have to sparge for 90 minutes, which works well for me.

-a.

Regarding the crush, I read a very compelling report with pictures by Breiss that indicated the crush is not important AT ALL with respect to extraction of sugars. In fact, they recorded fair extraction without crushing at all. This is the opposite of what is stated here repeatedly. See this post and the related links: http://www.homebrewtalk.com/f36/any-...3/#post4061244

I bought iodine when I first started brewing. It would register conversion in about 20 minutes. I haven't used it in years since it always converted.

An interesting read but I'm not convinced that his conclusions are valid for BIAB. His sample tested negative for starch at 40 minutes. Mine tested negative at 7 minutes. Quite a difference.

He does show a gain of fermentability with more time but such a small gain for the extra time that I'd wonder if nearly all of the conversion including the breakdown of the longer chain sugars happened much earlier than the 2 hours and just a difference in the yeast gave those results.

The software I've been using assumes a 75% attenuation with a 60 minute mash. I've been doing a 30 minute mash and getting higher attenuation than that, probably nearer to 80 to 85% attenuation. Shouldn't I be getting less attenuation with that short mash?

An interesting read but I'm not convinced that his conclusions are valid for BIAB. His sample tested negative for starch at 40 minutes. Mine tested negative at 7 minutes. Quite a difference.

He does show a gain of fermentability with more time but such a small gain for the extra time that I'd wonder if nearly all of the conversion including the breakdown of the longer chain sugars happened much earlier than the 2 hours and just a difference in the yeast gave those results.

The software I've been using assumes a 75% attenuation with a 60 minute mash. I've been doing a 30 minute mash and getting higher attenuation than that, probably nearer to 80 to 85% attenuation. Shouldn't I be getting less attenuation with that short mash?

I've got no answers. Honestly, I don't care, either. I use a refractometer to make sure my OG into the ferementor is exactly what I want. But of course I don't want to pass on bad info, so I do appreciate you posting your experience here.

There's a thread buried on here somewhere with experiments showing conversion in around (as little as) 10 minutes. I'm not sure if Kai's method actually included tests for <40 minutes or not based on his wording. All in all, it seems like a fairly conclusive scientific method he used. How do you think BIAB conclusions would be different?

Regarding the crush, I read a very compelling report with pictures by Breiss that indicated the crush is not important AT ALL with respect to extraction of sugars. In fact, they recorded fair extraction without crushing at all. This is the opposite of what is stated here repeatedly.

I bought iodine when I first started brewing. It would register conversion in about 20 minutes. I haven't used it in years since it always converted.

I wonder about the report that crush is not important as when people have poor efficiency, we tell them to crush better and their efficiency goes up. Why such differences in the results? Why is the definitive extract potential measured in a congress mash where the grains are ground to flour instead of left whole? Things are not adding up.

Some day I may have to try that, mashing some uncrushed grain and then cutting open a kernel after the end of the mash to see if it got wet to the center, if it has any starch left in that kernel, and if the kernel is sweet, indicating that the sugars were not extracted.

I may have to try the iodine test again too just to see how quickly the conversion occurs. Since my test said I had conversion in 7 minutes, where do I have partial conversion.

There's a thread buried on here somewhere with experiments showing conversion in around (as little as) 10 minutes. I'm not sure if Kai's method actually included tests for <40 minutes or not based on his wording. All in all, it seems like a fairly conclusive scientific method he used. How do you think BIAB conclusions would be different?

To get conversion from starch to malt sugar you need to get the grain particles wet to the center. Any part of the kernel that doesn't get wet doesn't convert but you don't extract either starch or sugar from it either. With my BIAB, I grind the grains quite fine. I'm pretty sure that helps the particles wet. My measured efficiency says so too. Maybe more of us need to experiment with this and use different crush/grind to see how it changes.

I edited and added the link above, but here you go anyway. It's a little hard to understand what the numbers in the table mean, but the point is that they got great efficiency from everything that that was crushed at all.

I edited and added the link above, but here you go anyway. It's a little hard to understand what the numbers in the table mean, but the point is that they got great efficiency from everything that that was crushed at all.

Nice table. So without crushing at all they got 24% efficiency. Not too unexpected as soaking the grains will wet them eventually and you can leach the sugars out some. The question I have is the length of time that it takes to get 94% efficiency with the coarse milling. That doesn't seem to be available info. Do they do a 30 minute mash, 60 minute, 90 minute, or are they talking 24 hours? I don't want to wait for a long mash, I expect to get my beer brewed and get on to other jobs. I seem to get great efficiency with a fine grind and a 30 minute mash and I get very good attenuation which makes me think I got the right mix of long and short chain sugars too as if all I got were long chain my attenuation would suffer. Lots of questions, hard to find solid answers to many of them.